Signal generator apparatus



Oct. 6, 1959 D. l.. JAFFE 2,907,962

" SIGNAL GENERATOR APPARATUS AFilm1 Feb. 11, 1953 s sheets-sheet 1 v La BLowER INI/ENTOR.

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Oct. 6, 1959 l D. L. JAFFE 2,907,962

' SIGNAL GENERATOR APPARATUS Filed Feb. 11. 195s :sheets-she@ 2 fu in m" E@ INI/ENTOR.

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D. L. JAFFE 2,907,962/

SIGNAL GENERATOR v.PPRATUS Oct. 6, 1959 l Filed Feb. 11, 195s' s sheets-sheet a SIGNAL GENERATOR APPARATUS David Lawrence Jaire, Maspeth, N.Y., assignor to Polarad Electronics Corporation, Brooklyn, N.Y., a corporation of New York Application February 11, 1953, Serial No. 336,359

4 Claims. (Cl. S33-82) The present invention relates to improvements in signal generator apparatus, and more particularly to such apparatus using the cavity resonator type oftu-ned circuits,

'such as are customarily associated with reflex klystron tubes or the so-called light house tubes used for ultrahigh-frequency and microwave systems.

lIn the construction, design and use of such tubes, an important problem is the dissipation of heat unavoidably generated during the operation of the device. As greater and greater powers are developed in such tubes, more and more heat is created, which must be dissipated in order to avoid harmful effects upon the apparatus and upon the tube. According to one aspect of the present invention, improved apparatus is provided which is designed for simple and eiiicient use with forced air cooling, the provision for such cooling being combined with other features providing improved electrical operation of the oscillator or signal generator itself.

Another problem encountered in signal generators of this type is that of providing wide-range tuning. According to another feature of the present invention, improved tuning means is provided for the cavity resonator associated with the tube to permit adjustment of its frequency of operation over a wide band and without introducing harmful effects due to undesired modes of oscillation or contact resistance. For this purpose, the present invention provides novel mode Suppressors and improved adjustable short-circuiting means for coaxial-type cavity resonators.

According to another feature of the present invention, such short-circuiting means includes impedance matching wave traps or chokes which are further improved by reducing their size and broad banding their frequency characteristics by the addition of dielectric material lling the resonant space of such traps or chokes and by adding energy-absorbing means in association therewith.

These and other features and advantages of the present invention will become more fully apparent from consideration of the following detailed description of a preferred embodiment thereof in association with the appended drawings, wherein Fig. l shows a longitudinal cross-sectional elevational "ice vention is applied to an electron tube'11 adapted to be associated with a cavity resonator generally indicated at :'12 and preferably of the coaxial type having an outer cylindrical member 13 and an inner cylindrical member 14 in conjunction with a slidable shorting plunger 1'6 which effectively interconnects and short circuits the two cylindrical members 13 and 14 at the inner face (on the left as viewed in Fig. 1) of the shorting plunger 16. The details of this shorting member 16 are described hereinbelow.

.The tube 11 may be a reflex klystron, such as the 5721 type, or may be any other type of tube adapted to be used with a cavity resonator, such as a light house tube, ultra high frequency tube, or the like.

At the left of Fig. l is shown a housing 17 containing a conventional socket or connections for the tube 11,` the details of which form no part ofthe present invention and hence are not disclosed. This housing 17 may be clamped to the tube 11 by a clamping arrangement 18 whose details are also immaterial hereto.

For lthe purpose of adjusting the frequency of the output of the present device the shorting plunger 16 is secured to a pair of rods 19 which in turn are secured to a movable member A21 whose position relative'to the resonator structure may be adjusted by means of the tuning arrangement generally indicated at 22. f

The tube 11, shown as a reflex klystron, has two annular resonator terminals contacted respectively by the resonator members 13 and 14. It also has a reector terminal 23 which must be supplied with suitable voltage. For the purpose of making connection to the terminal 230i the tube 11, it is secured to a spring 24 and thereby to a wire 26 contained within a hollow cylinder 29 xed to member 21 and movable with it. Cylinder 29 slides within resonator cylinder 14, and to prevent accidental electrical contact between spring 24 and cylinder 14, an insulating sleeve 30 is secured to cylinder 29 surrounding spring 24, and a further insulating sleeve 35 is ixed within cylinder l14 in telescoping relation to sleeve 30.

To complete the enclosure of the resonator and to l prevent any possible energy leakage because of the tuncumference of wallv 13 by an arc of substantially 90 deview of the entire signal generator of the present invention;

Fig. 2 shows an end elevation view of the device of Fig. l viewed along line 2 2 thereof;

Fig. 3 shows a fragmentary top plan view of the device;

Fig. 4 shows a cross-sectional view taken along line 4 4 of Fig. 1;

Fig. 5 shows an enlarged cross-sectional view along line 5 5 of Fig. l, showing a face view of the shorting plunger;

Fig. 6 is a fragmentary longitudinal cross-sectional view of the resonator and shorting plunger taken along line 6 6 of Fig. 5; and

Fig. 7 is a similar fragmentary view taken along line 7 7 of Fig. 5.

Referring to the drawings, one form of the present ingrecs. Thus, these slots 27 are non-symmetrical with respect to the axis of the resonator and this feature becomes important particulanly with respect to suppression of the undesired TEM mode of oscillation, which is otherwise easily produced in such a resonator by any irregularity of structure. In order to avoid leakage of energy and consequent ineiiiciency and damping of the oscillation within the resonator, the slots 27 are covered external-ly of the resonator by hollow channels 28. These channels 28 are closed at one end 53 but are open at the dicated above, it is necessary in the operation of such tubes for proper provision to be made for dissipating the heat internally generated. This is especially important where the cavity'resonator is external to the tube and surrounds it, as here, so that normal heat dissipation by radiation is inhibited. To provide proper cooling for heat dissipation, the present invention relies upon forced air circulation. A tubular member 56 is provided which communicates with the interior of the resonator adjacent the electron tube 11. Member 56 is coupled to a suitable blower or fan, not shown, which can force air therethrough into the resonator. This cooling air can then escape through slots 27 and channels 2S, whereby these elements have simultaneously the electrical function of preventing spurious resonances and energy leakage, and the cooling7 function of providing the air outlet. The tubular member 56 is dimensioned internally to operate as a below cut-off wave guide yat the operating frequencies so that no radiation is propagated therealong and thereby lost.

Another feature of the present invention resides in the improved form of shortacircuiting plunger 16 utilized herein, which is shown more in detail in Figures 5, 6 and 7. This short-circuiting plunger 16 electrically interconnects the outer resonator cylinder 13 and the inner resonator cylinder 14 to complete the resonator, and its position determines the resonant frequency of the resonator and hence the operating frequency of the device. Tuning of the device is effected by `adjustment of the position of this plunger 16 as already described.

The plunger 16 is formed by a series of rings, sleeves and insulating inserts forming -a unitary assembly. lt comprises a metallic ring 31 formed with an `axially extending sleeve 32 whose outer diameter is slightly less than the inner diameter of cylinder 13. The drive-rods 19 'are `secured to the ring 31 in any suitable fashion. The ring 31 is secured to a sleeve 33 having an inner diameter slightly greater than the outer diameter of cylinder 14 and joined integrally with a disk 34 having a coaxial ange 36, and defining an `annular space between the disk 34, the ring 31, and the sleeves 32 and 33, this annular space being open at its outer edge through a nar- `row annular gap as at 37. Within this annular space there is positioned an insulating insert 3S of annular shape which completely fills the space. Joined to the ange 36 as an extension of it is a further sleeve 39, joined to a disk or ring 41 having a further sleeve extension 42 whose inner diameter is slightly larger than the outer diameter of resonator cylindrical wall 14. A second annular space is defined between the disks 41 and 34 and the sleeves 39 and 42, this `annular space being Open at the annular gap 4t) in the inner cylindrical surface of the plunger. The second annular space is also filled by an insulating insert 43. An insulating sleeve formed in two parts 44, `46 is inserted between the resonator cylinder wall 14 and the sleeves 33 and 42. A similar insulating sleeve formed in two parts 47 and 48 is inserted between the outer resonator cylinder wall 13 and the sleeves 39, 36 and 32. These insulating sleeves are essentially bearing sleeves since they are joined to the plunger assembly and provide sliding non-metallic contact or bearing surfaces with respect to the relatively stationary resonator cylinder walls 13 and 14.

In electrical function the `arrangement thus far described provides a type of shortcircuiting device sometimes called a choke joint. The annular spaces filled by the vinsulating inserts 38 and 43 are designed to be resonant at a frequency within the range covered by the operation of the device. The outer cylinder wall 13 in conjunction with the sleeves 39 and 36 forms a quarter wave transmission line section, which serves as an impedance transformer to transform the very high impedance of the resonant cavity within which the insert 38 is placed to a very low impedance at the inner edge of the insulating bearing surface 47, providing an elec- 4' trical short-circuit at this location. Similarly, the high impedance of the yresonant cavity within which the insulating insert 43 is located is transformed to a low impedance at the inner gap between the inner cylinder wall 14 `and the plunger 16.

The use of insulation or dielectric in the present device provides a number of advantages. the resonant cavities of the choke joint with dielectric material, such as Teon, the physical size of these cav,-Y ities may be reduced to practical limits. Furthermore, the bearing sleeves 44, 46 and 47, 48, provide the dual function 0f providing good sliding surfaces, thereby reducing wear and friction, and of providing a proper characteristic impedance for the transmission line sections defined by the metallic surfaces bordering these sleeves on their outside and inside, for proper impedance transformation.

As a further feature of the present invention and to further reduce any leakage which may have occurred at or through the dielectric gaps between the plunger 16 and the inner and outer cylinder walls 13 and 14, an energy-absorbing ring 49 such as of polyiron or the like is suitably secured to the outer face of the ring 31, as by cementing or the like.

As another feature of the present invention, provision is made for extending the usable frequency range for such a choke joint. For this purpose theV inner face of the plunger 16 is formed with a series of radial slots such as 61 passing through disk 41. These radial slots are filled or lined with energy absorbing material such as Uskon For example, Uskon having a resistivity of 200 ohms per square may be used. This material fills or lines the slots 61 completely and serves both to dampen undesired modes of oscillation within the main cavity and to prevent leakage of energy from the main cavity by way of the gaps between the plunger 16 and the cylindrical walls of the main cavity, over wide ranges. of frequency, thereby extending the useful range of frequencies of operation of the device.

What is claimed is:

l. A cavity resonator designed for operation over a predetermined range of frequencies having a cylindrical outer wall and a coaxial cylindrical inner wall, said outer wall being formed with a plurality of mode-suppressing slots extending parallel to the axis thereof and spaced, unsymmetrically around the circumference of said outerl wall, whereby TEU mode oscillations in said cavity are suppressed, and respective channel members covering said slots on the exterior of said outer wall, each of said channels having a closed end adjacent one end of its slot and an open end spaced from the other end of its slot by a distance greater than one wavelength at any operating frequency in said predetermined range, said channels having cross-sectional dimensions unsuited to propagate radio waves at any operating frequency, a tubular member communicating with the interior of said cavity resonator and having a crossasection unsuited to propagate radio waves at any operating frequency, and means for supplying cooling fluid to said resonator through said tubular member, said slots and channels serving as exits for such fluid.

2. A cavity resonator designed for operation over a predetermined range of frequencies having a cylindrical outer wall and a coaxial cylindrical inner wall, said outer wall being formed with a plurality of mode-suppressing slots extending parallel to the axis thereof and spaced unsymmetrically around the circumference of said outer wall, whereby TE11 mode oscillations in said cavity are suppressed, and respective channel members covering said slots on the exterior -of said outer Wall, each of said channels having a closed end adjacent one end of its slot and an open end spaced from the other end of its slot by a distance greater than vone wavelength at any operating frequency in said predetermined range, said channels having cross-sectional -dimensions unsuited to Thus, by filling propagate radio Waves at any operating frequency in said predetermined range, and means for supplying cooling fluid to said resonator, said slots and channels Serving as exits for such fluid.

3. A cavity resonator designed for operation over a predetermined range of frequencies having a cylindrical outer Wall formed with a plurality of mode-suppressing slots extending parallel to the axis thereof and spaced unsymmetrically around the circumference of said outer wall, whereby TEM mode oscillation in said cavity are suppressed, and respective channel members covering said slots on the exterior of said outer Wall, each of said channels having a closed end adjacent one end of its slots and an open end spaced from the other end of its slot by a distance greater than one wavelength at any operating frequency in said predetermined range, said channels having cross-sectional dimensions to propagate radio waves at any operating frequency in said predetermined range, said slots and channels serving as exits for cooling uid which is supplied to the resonator.

4. A signal generator for use with an electron tube having a cap terminal and a pair of annular terminals, said generator comprising a cavity resonator designed for operation over a predetermined range of frequencies having coaxial cylindrical inner and outer walls defining a cavity and adapted to be coupled respectively to said annular terminals, a connection for said cap terminal passing substantially coaxially through said inner wall cylindrical member, said outer wall having a plurality of mode-suppressing slots extending parallel to the axis thereof and spaced unsymmetrically around the circumference of said outer wall, respective channel members covering said slots on the exterior of said outer wall, each of said channel members having a closed end adjacent one end of its corresponding slot and an open end spaced from the other end of its corresponding slot by a distance greater than one wavelength at any operating frequency in said predetermined range, a cooling fluid inlet tube communicating with the interior of said cavity, said inlet tube and channel members having cross-sections unsuited for propagation of radio waves therealong at any operating frequency in said predetermined range, means coupled to said inlet tube for causing cooling iluid to pass through said tube into said cavity and outwardly through said slots and channel members, a sliding plunger adjustably interconnecting said inner and outer walls, a disk tuning member coupled to said plunger for movement therewith, and a flexible bellows coupling and said tuning member to said outer member for minimizing radiation leakage past said tuning member and plunger.

References Cited in the le of this patent UNITED STATES PATENTS 2,104,554 Conklin Jan. 4, 1938 2,197,122 Bowen Apr. 16, 1940 2,203,806 Wolf June 11, 1940 2,395,560 Llewellyn Feb. 26, 1946 2,399,930 Keister May 7, 1946 2,446,405 Bels Aug. 3, 1948 2,487,547 Harvey Nov. 8, 1949 2,495,733 Kandoian Jan. 31, 1950 2,512,468 Percival June 20, 1950 2,543,721 Collard et al. Feb. 27, 1951 2,560,536 Althouse July 17, 1951 2,593,095 Brehm Apr. 15, 1952 2,593,155 Kinzer Apr. 15, 1952 2,623,194 Jenks Dec. 23, 1952 2,644,889 Finke et al. `Tuly 7, 1953 2,697,138 Balthis et al Dec. 14, 1954 2,706,802 Meisenheimer et al. Apr. 19, 1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION October 6, 1959 Patent No. 2,907,962

David Lawrence Jaffe It is herebjf certified that error appears in the printed specification of the above numbered patent requiring correction and 'that Jshe said Letters Patent should read as corrected below.

"osoillatiom read os strike ou'l'J "and" Column 5, line lO, for

column 6, line 13,

Signed and sealed 'this 5th day of April 1960.

(SEAL) Attest:

ROBERT C. WATSON 

